Sonic energy metal working process

ABSTRACT

Utilization of a resonant electromechanical transducer for delivering high power (energy to a nonresonant load surface, excited from a fixed frequency power supply. The application of the tool to the work surface is accomplished by a flat surface tool coupled perpendicular to the horn axis and parallel to the end surface of the transducer tip. The sonic energy is delivered to the workpiece by coupling only a small fraction of the total tool surface to the work surface. The velocity of the cutting surface of the tool relative to the workpiece is a function of the excitation level of the transducer; the velocity being independent of the average velocity by which the transducer is moved across the work surface. The rate of removal of material in a metal cutting, chip forming, or shaving operation is a function of the excitation and the depth of cut independent of the transducer-transfer-velocity; whereas, outside of certain limits the transducer-transfer-velocity is utilized to reduce the cutting rate of the tool.

' United States Patent 1191 v McDaniel {22 Filed:

. [21 Appl. No.: 150,957

[541 some ENERGY METAL woruuuo rnocsss- [75] Inventor: Raymond Ci McDaniel, Columbus,

73 Assignee: The 01110 sum University,

Columbus, Ohio 1 June 8,1971

[s2] Us. (:1 90132; R, 51/59 SS, 82/DIG. .9,

714,860 9/l954 Great Britain 82/DlG. 9

'AUTOMATIC/ a l VERT'CAL 1451 Aug. 28, 1973 Primary Examiner-FrancisS. Husar I l Attorney-Sidney W. Millard, William D. Freeland el al.

[5 7] ABSTRACT Utilization of a resonant electromechanical transducer for delivering high power (energy to a nonresonant load surface, excited from a fixed frequency power supply. The application of the tool to the work surface is accomplished by a flat surface toolcoupled perpendicular to the horn axis and parallel to the end surface of the transducer tip. The sonic energy is delivered to the workpiece by coupling only a small fraction of the total tool surface to the work surface. The velocity of the cutting surface of the tool relative to the workpiece is a function of the excitation level of the transducer; the velocity being independent of the average velocity by which the'transducer is moved across the work surface. The rate of removal of material in a metal cutting, chip forming, or shaving operation is a function of the excitation and the depth of cut independent of the transducer-transfer-velocity; whereas, outside of certain limits the transducer-transfer velocity is utilized to reduce the cutting rate of the tool.

7 Claims, 5 Drawing Figures FEED 11111111..."" W1111111111.11;; """U lil 1. illlllllllmX/l I Patented Aug. 28, 1973 2 Sheets-Shoat .l.

INVENTOR. RAYMOND 0. Mc DANIEL fennamo JC'mZ/aJ 8 oal" ATTORNEYS 2 Sheets-Sheet 2 INVENTOR RAYMOND C.Mc DANIEL Cennamo JCmL M 7 305!" ATTORNEYS 1 SONIC ENERGY METAL WORKING PROCESS BACKGROUND There is disclosed by Robert C. McMaster, et al., in

' U.S. Pat. No. 3,368,085, dated Feb. 6, l968,forSonic Transducer and assigned to The Ohio State University, an electromechanical transducer of the same class as the present invention. This patent describes a trans ducer which is a combination of a driving piezoelectric element and a mechanical displacement horn amplifier. In principle, the transducer utilizes a static compressive force to bias the piezoelectric driving element. Under dynamic excitation the piezoelectric elements are not stressed in tension but operate under compression. Thus the stress during operation will range between a trated there, does not directly contact the workpiece.

A second solution to the frequency shiftproblem is disclosed in copending patent application, Ser. No. l,957, filed Mar. 4, 1970, for Sonic Transmission Line, by Charles C. Libby and Karl Graff, and now abandoned for continuation application Ser. No.

, 122,219. In that system a transmission line having a minimum compression stress and its maximum allowable stress. The maximum limit on the compressive stress in the driving element is dictated by the stress at which depolarization occurs.

In an over-all analysis of the McMaster' transducer the full capabilities of the materials are utilized by a balanced design. No one part alone of the design limits the capacity of thetransducer; but rather asmany parts as feasible work to their maximum capability. This fact plus the minimum resonant over-all length reduces the required volume and weight. The result is that high horsepower output per pound of transducer material is made possible.

In the U.S. Pat. No. 3,368,085, there isdi'sclosed a variety of mechanical displacement amplifiers, com monly referred to as horns more accurately defined as force concentrators. The variety of mechanical displacement amplifiers encompasses the many shapes each operable for an intended purpose.

In the copending patent application. Ser. No. 541, filed Jan. 5, 1970, for Electromechanical Transducer by R. C. McDaniel, and assigned to The Ohio State University, there is disclosed an improved transducer over that disclosed in the prior issued patent. This ap-' plication shows yet another shapefor a mechanicaldisplacement amplifier. In this embodiment it is valve shaped.

Of the prior art transducers purportedly capable of high power output there was an acknowledged'inability to transfer the high power energy to the workpiece. Resonant types of electromechanical transducers when excited at the resonant frequency are capable of high power energy; but, at a no-load free space. When a load is applied the power capabilities are so drastically reduced that the transducer is practically useless. It has been found that a significant reason for the loss of power is that the load itself,-i.e., workpiece, becomes part of the resonant structure. With a shift in' the'resonant frequency of the transducer, exciting the transducer at its original resonant frequency is'almost of no avail.

Although the shift in resonant-frequency became known, its solution did not. The most common-manner of coping with the situation was to measure the frequency shift and then to shift the frequency of the excitation source. This method issomewhat operable if sufficiently sophisticated equipment is used. But the size and cost of the equipment is clearly out of line with the results obtained.

In the US. Pat. No. 3,475,628, for Sonic Transducer Apparatus, by Robert C. McMaster, I-Iildegard M. Minchenko, and Charles'C. Libby, and assigned to predetermined length directly connects the energy to the workpiece without a loss in power.

Still another solution to the frequency shift problem is disclosed in U.S. Pat. No. 3,558,937, for Sonic Transducer Apparatus, by R. C. McMaster', et al. In that system a transmission line directly couples the concentrated energy to a workpiece without a shift in frequency. The distinction being that the transmission line is at an angle relative to the plane of the workpiece.

SUMMARY OF THE INVENTION The apparatus and system of the present invention is capable of delivering high power energy from a resonant electromechanical transducer to a nonresonant load surface from a fixed frequency source. A tool is rigidly attached to the tip of the force concentrator (horn) of the transducer. The tool has a flat face perpendicularly positioned with respect to the axis of the transducer from. The high power energy is coupled to the work surface with only a small fraction of the total tool surface. Thereby the constant-frequency capabilities of the system is related to the configuration of the surfaces and the fraction of the coupling of the tool with the surface of the workpiece.

The velocity of the cutting surface of the tool and the cutting rate of the tool are also related.

OBJECTS It is accordingly a principal object of the present invention to provide a new and improved resonant electromechanical system in a work enviornment.

Another object of the invention is for a resonant electromechanical system operable to utilize high power energy from a constant-frequency system.

Another object is for a resonant electromechanical system operable in a metal cutting, chip forming or shaving operation. 1

,Another object is for a resonant electromechanical system in a wo'rkenviornment wherein the velocity or cutting rate of a cutting tool is controlled.

Still another object of the present invention is to provide a resonantelectromechanical system in a metal working environment which is simple, straight forward and relatively inexpensive.

Other objects of the invention will become apparent when taken in conjunction with the drawings, of which:

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an isometric view of the system apparatus operable in accordance with the principles of the pres ent invention;

FIG. 2 is a breakdown component arrangement of FIG. 1;

FIG. 3 and 3A are alternatively shaped cutting tools; and

FIG. 4 is a graphical representation of the depth of cut versus the angle between the tool and the surface of the work material.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIG. 1 there is shown the transducer of the aforesaid Ser. No. 541, patent application in a work environment in accordance with the concepts of the present invention. The particular operation shown is that of a metal cutting operation; however, it will be apparent to those skilled in the art that the invention is not so limited. 7

The transducer 10 has its energizing voltage applied to a pair of internally positioned piezoelectric wafer elements (4 and 5, FIG. 2). The coaxial cable 24 feeds the voltage to a pair of electrodes adjacent the piezoelectric wafer elements via handle 25 and a connector also internally positioned. A clamping ring 14 and the supporting assembly 16 having handles 25 and 30 positioned thereon, structurally supports, in a mechanically sealed manner, the piezoelectric wafers. The clamping ring 14 and-the supporting assembly 16 are integrally formed in the nodal region. The force concentrator20, sometimes'refereed to as the horn, has tool 40 fixedly positioned at its point of maximum amplitude.

Referring also to FIG. 2 showing the breakdown somewhat to scale the component arrangement of FIG. I, the force concentractor 20 is valve-shaped in contrast to the more commonly tapered shape. The force concentrator 20 is positioned in the over-all structure so that its reduction in size, i .e., from the cap 7 tostem 8, occurs below the nodal region of the overall resonant sonic structure. Other structural details are disclosed and described in the copending patent application, Ser. No. 541. In accordance with the concepts of the present invention, the tool 40 is fixedly positioned on the tip of the stem 8 of the force concentrator 20 for free contact of the tool 40 with the work surface 1 1.

It is to be noted specifically that the tool 40, i.e., that which engages the work surface 11, does not have an over-all cutting shape; to the contrary, it is flat faced. The flat surface 42 of the tool 40 is an end face of a caplike structure threadingly, or otherwise fixedly, positioned at 43 to the end or tip of the stem 8 of the force concentrator 20. The flat surface 42 of the tool 40 is therefore positioned perpendicular to the tip of the end surface of the force concentrator 20.

It is apparent,therefore, from the above-described tool, that no intermediate impactor is utilized yet the energy from a resonant transducer into a nonresonant work surface may be delivered from a fixed frequency supply. The high level sonic energy is delivered to the work surface by direct. coupling to the work surface, but only contacting'a small fraction of the total tool to the work surface. The work function at high energy levels is accomplished by the sonic energy being reflected at either end of the system from flat surfaces, parallel to one another, and on one axis. Accordingly, the constant frequency system, wherein there. is no appreciable shift in resonant frequency of the transducer, is maintained by theconfiguration of the surface.

With further reference to FIG. 1 there is illustrated the theoretical operation of the system of the present.

invention by the arrows. Specifically the arrow DSF illustrates the direction of the static force which controls the depth of cut. The arrow DTT illustrates the direction of the transducer travel note particularly that v the transducer is pulled along the work surface in contrast to pushed. The arrow DTM illustrates the direction of sonic movement of the vibrating tool 40 attached to the transducer force concentrator 20. Finally, zone A indicates the major zone of cut metal flow and zone B the minor zone of cut metal flow. Again note that the majority of the cut metal is forward of the transducer and is opposite in direction to the movement of the transducer.

There is further illustrated in FIG. 1 an automatic feed system for uniform relative movement between the transducer 10 and the work material surface 11. The automatic feed 50 is linked, via linkages 53 and 55, to the top end of the transducer 10. The linkage supports the transducer and further supplies what little static force is necessary. It can be appreciated, of course, that the transducerv I0 may be fixed in position i and the work material 11 moved relative to the transway of the automatic feed 50 across the fixed work surface 11. A static force is applied as shown by arrow DSF by means of a vertical-feed adjustment 57 to the linkages 53 and 55 to the transducer 10. In this way the transducer 10 is sprung against the work surface.

As the vibrating transducer tool 40 is pulled slowly along the metal surface 11, the vibrating tip pushes or cutsthe metal into a continuous ribbon or chip, by the much faster reciprocating motion of the vibrating tool. The majority of the cut metal from the surface 1 1 came out in chips or strips from behind the tool zone A and some in front of the tool in zone B. As shown in the graph of FIG. 4, as the angle of the transducer to the plate was increased (with the vertical feed set the same each time) the depth of cut was increased. The graph of FIG. 4 also shows that the depth of cut is a function of tool configuration and the spring in the system since all points plotted were at a constant vertical setting of 030i per cut. The depth of successive cuts were reproducable to i 0.001 inch when re peated with all parameters the same. I

Although the flat face is operable as intended special work functions or applications may better be formed with a substantially flat face but with a specific cutting edge. The average power input during these tests was 200 watts. The maximum power input was 440 watts during one test when the depth of cut was 0.37 inch. Based on typical operating conditions longitudinal tool oscillation has been measured to be 0.003 inch peakto-peak.

FIGS.'3 and 3A illustrate two other than completely flat surface tools that may be utilized. The operation has theadvantage of being self relieving since-the necessary downward static force is applied through a spring system and any excessive horizontal feed rate results only in less metal removed with no damage to equipment. The compliance of the horn extension (springiness in flexur e) provides the spring action.

Most significantly, it is the velocity attributable to the acoustic motion of the tool tip, that provides the cutting action. In other words, it is the rapid reciprocating or sinusoidal sonic motion of the tool that provides the In a typical operation, the transducer 10 is pulled by cutting action. It is not the relatively slow, average velocity of the transducer across the work surface, that determines the chip-forming-velocity. At any one frequency, this rapid sonic velocity is independently controlled by the transducer excitation. Increasing the average velocity or the gross motion of the transducer, as it moves across the work surface, actually reduces the rate of metal removal. This is contrary to the case of the conventional lathe, shaper, planer, etc. in which an increase of the average velocity, of the tool across the work surface, causes an increase in the volume of metal removed. It is also contrary to published information on sonic metal-cutting process. An increased hardness of the work surface, as cutting continues, does not cause an increase in the forces acting on the tool as drag force is maintained substantially the same in this unique process. E

Although certain and specific embodiments have been shown, it is to be understood that modifications may be had without departing from the true spirit and scope of the invention.

What is claimed is:

l. A resonant horn structure electromechanical transducer comprising a loading mass having a first elongated structure of relatively fixed diameter, a force concentrator consisting of a second elongated structure of a lesser diameter, a piezoelectric driving means, and a clamping means; said driving means being positioned between one end face of each of said first and second elongated structures and defining a location of lower velocity, said clamping means consisting of a ring element engaging the said end faces; and the other end of said force concentrator elongated structure remote from said driving means defining a location of maximum velocity, said last named endhaving a flat surface in a plane perpendicular to the longitudinal axis of said force concentrator elongated structure; a tool having a flat surface, and means for fixedly positioning said flat surface of said tool parallel with the flat surface of said other end of said force concentrator elongated structure.

2. The transducer of claim 1 further comprising means for pulling said tool face across said work surface.

3. The transducer of claim 2 wherein said last-named means further includes means for applying a static force to said work surface.

4. The method of sonically removing metal from a flat work surface with a tool sonically vibrated by a resonant horn structure electromechanical transducer comprising: defining a location of maximum velocity, providing a flat surface at said location, positioning said flat surface in a plane perpendicular to the axis of said structure, providing said tool with a flat surface, positioning said flat surface of said tool parallel with said flat surface at said location of maximum velocity, contacting only a small fraction of said tool with a work surface and varying the angle between the flat tool surface and said work surface to thereby vary the depth of cut of said tool into said work surface. I

5. The method of claim 4 further providing the step of pulling said tool across said work surface.

6. The method of claim 4 further providing applying a static force to said work surface.

7. The method of claim 6 wherein said step of applying static force includes applying said static force through a spring system. 

1. A resonant horn structure electromechanical transducer comprising a loading mass having a first elongated structure of relatively fixed diameter, a force concentrator consisting of a second elongated structure of a lesser diameter, a piezoelectric driving means, and a clamping means; said driving means being positioned between one end face of each of said first and second elongated structures and defining a location of lower velocity, said clamping means consisting of a ring element engaging the said end faces; and the other end of said force concentrator elongated structure remote from said driving means defining a location of maximum velocity, said last named end having a flat surface in a plane perpendicular to the longitudinal axis of said force concentrator elongated structure; a tool having a flat surface, and means for fixedly positioning said flat surface of said tool parallel with the flat surface of said other end of said force concentrator elongated structure.
 2. The transducer of claim 1 further comprising means for pulling said tool face across said work surface.
 3. The transducer of claim 2 wherein said last-named means further includes means for applying a static force to said work surface.
 4. The method of sonically removing metal from a flat work surface with a tool sonically vibrated by a resonant horn structure electromechanical transducer comprising: defining a location of maximum velocity, providing a flat surface at said location, positioning said flat surface in a plane perpendicular to the axis of said structure, providing said tool with a flat surface, positioning said flat surface of said tool parallel with said flat surface at said location of maximum velocity, contacting only a small fraction of said tool with a work surface and varying the angle between the flat tool surface and said work surface to thereby vary the depth of cut of said tool into said work surface.
 5. The method of claim 4 further providing the step of pulling said tool across said work surface.
 6. The method of claim 4 further providing applying a static force to said work surface.
 7. The method of claim 6 wherein said step of applying static force includes applying said static force through a spring system. 